The Efficient Home Forum

I'm about to install an HCC80R. I will be using a wireless link from this via the ATC928G3000 controller to the boiler which will be controlled by a BDR91A.
However although I probably won't use it I don't understand 'integrated boiler relay potential free contact 42V' Is this a relay on the HCC80R with isolated contacts that could be used to trigger the boiler? Is it a 42V potential supplied via this relay contact? If so why 42V? Is that what some boilers use? Will this trigger in addition to the wireless control signal sent?

Many thanks to you all for this extremely helpful forum.

The HCC80R is used for wider applications outside of evohome, so has options for several commercial and standalone applications too.

When used with evohome, it is simply used for wireless control of thermal actuators on multizone UFH manifolds and the UFH pump/zone valve. None of the other functions or quirky voltage applications are used.